The catch(es)

Firstly this involves overwriting the default launcher background, so be sure to make a backup first. Secondly, depending on your design, your launcher may stick out like a sore thumb since the main desktop panel is not ‘configurable’. Finally subsequent updates to Unity 2D will overwrite this again, so keep your created image handy also.

— Update —

Reader Sergey sent in a few tips that may be of use to those attempting this: –